1. Field of the Invention
The present invention relates to an electronic device housing for storing a plurality of electronic circuit packages each formed by mounting a plurality of electronic components on a printed wiring board.
2. Description of the Related Art
As a structure of an electronic device such as a communication device, computer, or switching device, it is known that a plurality of electronic circuit packages each formed by mounting electronic components such as ICs and LSIs on a printed wiring board are inserted into an electronic device housing having a back board and are plug-in connected to the back board. In the electronic device having such a structure, the electronic circuit packages are sometimes exchanged or added during the operation of the device for the purpose of maintenance or addition of function. In performing such working, it is necessary to prevent a reduction in cooling efficiency and improve the working efficiency. Further, it is also necessary to take electromagnetic shielding measures for preventing electromagnetic interference (EMI). Further, in response to an increase in size of the electronic device having such a structure, it is also necessary to prevent the deflection or deformation of the electronic device housing.
Referring first to FIGS. 13 and 14, there will be described an electronic device configured by using a conventional electronic device housing. The electronic device is generally composed of an electronic device housing 1 having a multi-stage structure and a plurality of electronic circuit packages 2 inserted in each stage of the electronic device housing 1 so as to be arranged in parallel. Each electronic circuit package 2 is generally composed of a printed wiring board 2a and a plurality of electronic components 2b such as ICs, LSIs, and a connector mounted on the printed wiring board 2a. The electronic device housing 1 is generally composed of a rack 3 having a unit frame and panels mounted on the unit frame except its front side, and a plurality of integral surface plates 4 for respectively shielding the front openings of all stages of the rack 3. Each integral surface plate 4 is detachably mounted on the rack 3 by screws 4a or the like. The electronic device housing 1 has in its each stage a plurality of pairs of upper and lower guide grooves 5. The upper and lower side edges of the printed wiring board 2a of each electronic circuit package 2 is guided by the guide grooves 5 in inserting the electronic circuit package 2 into the rack 3, and each electronic circuit package 2 is plug-in connected to a back board (not shown) mounted on a rear portion of the electronic device housing 1. In the following description, a plurality of sections of the electronic device housing 1 into which the electronic circuit packages 2 are inserted will be referred to also as slots.
A cooling fan is stored in an upper portion 6 of the electronic device housing 1. Reference numeral 7 denotes a reinforcing plate for preventing the deflection or deformation of the rack 3, which causes trouble in inserting or removing each electronic circuit package 2 or causes application of undue pressure to the electronic circuit packages 2 stored in the rack 3. In a normal operation, the integral surface plates 4 are mounted on the rack 3 to thereby make an electromagnetically shielded condition of the electronic device housing 1, and the cooling fan is operated to intake the outside air from the lowermost portion of the electronic device housing 1 as shown by an arrow A in FIG. 14, thereby preventing a rise in temperature inside the electronic device housing 1 due to heat generation from the electronic circuit packages 2. When the need for exchange, addition, or removal (which will be hereinafter referred to as exchange or the like) of any electronic circuit package 2 arises for maintenance, addition of function, etc., the corresponding integral surface plate 4 is removed to perform the working of exchange or the like by inserting or removing the electronic circuit package 2. Thereafter, the removed integral surface plate 4 is mounted again.
Referring next to FIGS. 15 and 16, there will be described an electronic device configured by using another conventional electronic device housing. Substantially the same parts as those shown in FIGS. 13 and 14 will be denoted by the same reference numerals, and the description thereof will be omitted. In this conventional electronic device housing, the integral surface plates 4 as shown in FIGS. 13 and 14 are not employed, but a package surface plate 8 is mounted on each electronic circuit package 2, and a blank plate 9 having a configuration similar to that of each electronic circuit package 2 or each package surface plate 8 is inserted in or mounted at each slot where the electronic circuit package 2 is not inserted.
The working of exchange or the like of the electronic circuit packages for maintenance, addition of function, etc. of the electronic device is sometimes performed while the electronic device is being operated. In this case, the conventional structure shown in FIGS. 13 and 14 has a problem such that the removal of the integral surface plate 4 causes electromagnetic interference due to cancellation of the electromagnetically shielded condition, or causes trouble due to insufficient cooling by a change in flow path of the cooling air as shown by an arrow B in FIG. 14. According to the conventional structure shown in FIGS. 15 and 16, the area of cancellation of the shielded condition through the front opening of the rack in exchanging or the like of the electronic circuit packages can be suppressed as compared with the conventional structure shown in FIGS. 13 and 14, thus preventing the occurrence of electromagnetic interference and the reduction in cooling efficiency to some extent; however, there is yet a room for improvement.
Further, in each of the above conventional structures, the integral surface plate or the blank plate must be removed and mounted in exchanging or the like of the electronic circuit package, causing an increase in number of working steps and a reduction in working efficiency. Further, while the reinforcing plate for preventing the deflection or deformation of the electronic device housing is mounted in each conventional structure, the presence of the reinforcing plate decreases the number of the electronic circuit packages allowed to be inserted, causing a hindrance to size reduction of the device. Further, the deflection or deformation of the electronic device housing cannot be enough prevented only by the reinforcing plate.